1. Field of the Invention
The present invention relates to door frame assemblies and particularly to prefabricated door frame assemblies.
2. Summary of the Prior Art
The use of prefabricated metal door frames has become quite common in both interior and exterior building construction and various different types of prefabricated frames and frame assemblies have been developed and used over the years. One of the more common types of prefabricated frames includes a frame member (which includes a web spanning the door opening in the wall and flanges extending from the edges of the web to circumscribe the opening), plus separate hinges and strike plates attached to the frame by conventional screw fasteners. Serious disadvantages of this type of prefabricated frame however, are the necessity of cutting the frame at the construction site to install the hinge plates and strike plate and the subsequent manual labor required to insert the numerous screw fasteners attaching the hinges and strike plates to the frame.
Other prefabricated door frames have been developed which avoid some of these problems but which have other disadvantages. In a frame such as that described in Cable, U.S. Pat. No. 3,299,592, the necessity of cutting the frame to install the hinges is avoided by providing counter-sunk areas or slots in the frame to which the hinges are spot welded. However, in the Cable frame, the hinges thus must be attached to the frame at the pre-set countersunk or slotted locations, preventing the convenient use of pre-hinged doors which may or may not have appropriately-located hinges. In addition, the existence of preset locations for the hinges requires the production of different models of the frame for left and right swinging doors.
In prefabricated door frame assemblies such as that depicted in Passovoy, U.S. Pat. No. 3,287,856, the frame assembly includes a frame member to which the hinges and strike plates can be attached at any location, plus cover plates attachable to the incomplete frame member to "finish" it where the hinges and strike plates are not attached. Although this assembly allows the use of pre-hinged doors, the use of conventional screw fasteners to attach the hinge and strike plates still requires considerable manual labor. A similar problem is encountered with the prefabricated door frame assemblies described in Yocum, et al., U.S. Pat. No. 3,783,559, and Cole, U.S. Pat. No. 3,774,345. The Yocum assembly, in fact, requires even more manual labor for installation because the cover plates, too, are attached by screw fasteners.
The prefabricated door frame assembly depicted in Passovoy, U.S. Pat. No. 4,236,354 minimizes the manual labor involved in installation of the assembly and allows the use of pre-hinged doors, but has other disadvantages. This assembly includes frame members having two transversely aligned parallel serrated slots to which prefabricated hinges having parallel serrated projecting tongues engageable with the slots are attached by inserting the tongues in the slots of the frame member. Similarly attachable cover plate sections and strike plates are also included. A problem with the Passovoy assembly, however, is that the hinge plates may tend to detach from the frame member, the tongues sliding out of the slots under stress.